The present invention relates to a printed circuit board used in electronic appliances and a method for manufacturing the printed circuit board.
To achieve low cost, compactness, and high performance in current electronic appliances, large numbers of circuit boards are used. In general, so-called "printed circuit boards" and also "ceramic circuit boards" are popularized as this circuit board. That is, in a printed circuit board, epoxy resin and the like containing glass fiber are used as a base material, and a conductive material is formed on this base material. In a ceramic circuit board, a ceramics material such as alumina is used as a base material, and a conductive material is formed on this base material.
In FIG. 13A to FIG. 13D, there is shown a general-purpose method for manufacturing a printed board. A photo-sensitive resist 132 is coated on an epoxy board 134 on which copper is plated on a surface thereof. This epoxy board 134 with the copper plating 133 is exposed via a photomask 131 (see FIG. 13A), and then is developed, so that a predetermined pattern is formed on the resist film (see FIG. 13B). Thereafter, a copper pattern portion which is not covered by the resist is etched away (see FIG. 13C) to remove the resist film, so that a conductor pattern is formed (see FIG. 13D).
Furthermore, when a multi-layer is formed, a plurality of boards on which the conductor patterns have been formed by the above-described method are overlapped with each other while sandwiching adhesive agents (so-called "prepreg") between them. The overlapped boards are pressured under a high temperature environment so as to be adhered to each other, resulting in a formation of a stacked layer. Thereafter, through holes are formed at preselected positions by using a drill. Next, electrical conductivities are established in the through hole portions by way of the chemical plating process, or the electrical plating process. Then, an outermost layer is formed by way of the photolithography stage and the etching stage.
On the other hand, as a method for manufacturing a ceramics board, ceramic powder is first mixed with an organic binder to manufacture a sheet called a "green sheet". A through hole is made in this green sheet by using a punching tool. After conductive paste is filled into this through hole, a pattern is printed on the green sheet by the conductive paste in a similar manner. Furthermore, a plurality of such sheets are overlapped with each other, and the overlapped sheets are sintered at a high temperature of more than 1,000.degree. C. by using a furnace to thereby manufacture this ceramic board.